The invention relates to a recording and/or reproducing apparatus as defined in the opening part of claim 1.
Information about a known recording and/or reproducing apparatus as defined in the opening part of claim 1 and information about a cassette with a magnetic tape as record carrier tape for such a recording and/or reproducing apparatus is obtainable via the internet, namely at the internet address xe2x80x9cwww.lto-technology.comxe2x80x9d. In connection with the known recording and/or reproducing apparatus and the known cassette reference may also be made to the two patent documents WO 98/44506 A2 and WO 98/44499 A1.
In the known recording and/or reproducing apparatus the disc-shaped drive member has drive teeth which form reel drive means at the drive member side and which serve and are configured to cooperate in a driving fashion with reel teeth of the supply reel of a cassette, which reel teeth form reel drive means at the reel side. During operation, when the cassette has been loaded into the recording and/or reproducing apparatus, the reel teeth and the drive teeth axially abut against one another, which is caused by the magnetic force of attraction of the magnetically acting holding means. The geometric distance in an axial direction between the first magnetic circuit element connected to the supply reel and the second magnetic circuit element connected to the disc-shaped drive member is in the first place dictated by the drive teeth and the reel teeth, but in the second place it also depends on the tolerances of said teeth as well as the tolerances of the axial dimensions of the two magnetic circuit elements and on the tolerances of the assembly dimensions of the two magnetic circuit elements. However, as a result of this dependence of the axial distance between the two magnetic circuit elements the magnetic force of attraction that occurs between the two magnetic circuit elements, which force depends on this axial distance, may vary comparatively strongly, which results either in a magnetic force of attraction which is inadequate for properly holding the supply reel on the disc-shaped drive member or in an excessive magnetic force of attraction, which may lead to problems when the supply reel is to be disengaged from the disc-shaped drive member, which disengagement is necessary when a cassette is moved out of the recording and/or reproducing apparatus. Tests have shown that in the case of an inadequate axial distance between the two magnetic circuit elements such a large magnetic force of attraction may occur that the supply reel of a cassette is no longer disengageable from the reel-shaped drive member of the recording and/or reproducing apparatus, or that such a large magnetic force of attraction is exerted on the first magnetic circuit element connected to the supply reel that the first magnetic circuit element may become disengaged from the supply reel. In both problem situations mentioned above the recording and/or reproducing apparatus requires a repair, which is unfavorable and undesirable.
It is an object of the invention to preclude the afore-mentioned problems with the aid of simple and reliable means and at low cost and to provide an improved recording and/or reproducing apparatus in which the occurrence of an undesirably large magnetic force of attraction between the first magnetic circuit element of a supply reel of a cassette and the second magnetic circuit element of the disc-shaped drive member is avoided.
To achieve this object, according to the invention, the characteristic features defined in the characterizing part of claim 1 are provided in a recording and/or reproducing apparatus as defined in the opening part of claim 1.
Owing to the provision of the characteristic features in accordance with the invention it is achieved in a simple manner that the magnetic force of attraction that occurs in operation between the first magnetic circuit element of the supply reel of a cassette and the second magnetic circuit element of the disc-shaped drive member of a recording and/or reproducing apparatus in accordance with the invention can never exceed a given value which can be defined by a suitable configuration of the magnetic-force-of-attraction limiting means, which consequently precludes the problems described hereinbefore for the known recording and/or reproducing apparatus.
In a recording and/or reproducing apparatus in accordance with the invention the magnetic-force-of-attraction limiting means may be formed, for example, by a separate element connected to the disc-shaped drive member, which connection may, for example, take the form of an adhesive joint. Such a construction is of particular advantage when the disc-shaped drive member is made of a magnetic or magnetizable material. However, in a recording and/or reproducing apparatus in accordance with the invention it has also proved to be very advantageous when, in addition, the characteristic features defined in claim 2 are provided. Such an embodiment has the advantage that it can be manufactured simply and has a high reliability. Such an embodiment, in which the magnetic-force-of-attraction limiting means are integral with the disc-shaped drive member, is particularly advantageous when the disc-shaped drive member is made of a non-magnetic or non-magnetizable material, notably when the disc-shaped drive member is made of a plastic.
In a recording and/or reproducing apparatus in accordance with the invention having at least one such projection it has proved to be particularly advantageous when, in addition, the characteristic features defined in claim 3 are provided. This guarantees an unambiguous, reliable and stable conformity with a given minimum distance between the first magnetic circuit element and the second magnetic circuit element.
In a recording and/or reproducing apparatus in accordance with the invention it has further proved to be very advantageous when, in addition, the characteristic features defined in claim 4 are provided. Such an embodiment has proved to be very advantageous in practice. Such an embodiment further has the advantages that as a result of the provision of the third magnetic circuit element the stray field of the magnetically acting holding means is kept comparatively small and that, in addition, a high efficiency of the magnetically acting holding means is achieved.
The above-mentioned as well as further aspects of the invention will become apparent from the embodiments described hereinafter by way of example and will be elucidated with reference to these examples.